Ottawa

'Frost quakes' crack ground, rattle homes across Ottawa

Some say they thought their children fell out of bed, while others thought something fell on their roofs. A meteorologist says it was actually the weather from the past 36 hours, which made a perfect recipe for a "frost quake."

People across Ottawa reported beds and walls shaking, hearing loud bangs and an 'explosion'

Residents across the city reported hearing loud bangs, jolting them awake in the middle of the night — a phenomenon that is likely a frost quake, according to a meteorologist. (Stu Mills/CBC)

It was a rude awakening for many. 

Across Ottawa, people were jolted awake at random intervals in the wee hours of Thursday morning. Loud bangs reportedly shook some beds and walls and led to sleepy-eyed searches throughout many homes — a collective experience, according to one meteorologist, that may be due to Mother Nature's perfect recipe for a phenomenon called a "frost quake."

"It had shook the entire house. It really did. I didn't know what was happening," said Emily Crocco, who lives in the city's east end suburb of Orléans. She recalled fearing for her family's safety after waking up to a loud bang shortly after 1 a.m.

I actually felt my bed and my walls shake.- Kirsten Hewson

"I have lived in this house for 11 years and had never experienced [that] before, so I was really worried."

Crocco said her partner experienced something similar in the past, and he called it an "ice quake." They are also called frost quakes, or cryoseisms — seismic events caused by soaked underground soils cracking after rapid freezing.

Still unsure, Crocco turned to her community Facebook page. Within the next few hours dozens of others described waking up and assuming either their partners or children had fallen out of bed, there was loud LRT construction, or someone broke into their homes.

Residents in the suburb of Barrhaven and in more rural areas also reported big bangs at their homes on social media over the past two days.

When Kirsten Hewson read Crocco's post, she breathed a sigh of relief after waking up panicked.

"It sounded almost like a cross between a small explosion and a giant thud of something hitting the foundation," said Hewson, who also lives in Orléans. She ran to check on her daughter and searched her home for signs of damage, only to find everything and everyone safe and sound.

Hewson says this is the first time she's heard about frost quakes, and she hasn't experienced anything like this in 16 years living there. 

"I actually felt my bed and my walls shake."

A meteorologist says frost quakes can happen with recent rainfall or snow melt, warmer temperatures leading to liquid seeping into the ground, followed by a re-freeze. (CBC News)

The perfect recipe for a frost quake

Steven Flisfeder, a warning preparedness meteorologist with Environment and Climate Change Canada, said Ottawa's temperature swings in the past 36 hours makes a frost quake possible across the city.

A perfect recipe for the frost quake includes either recent rainfall or snow melt, warmer temperatures leading to liquid seeping into the ground, followed by a re-freeze, "which certainly has occurred over the past couple of days in Ottawa," he said. 

According to historical data, temperatures across the city hit slightly above 0 C, and then dipped below –15 C in the past few days.

"When that occurs, that water that seeps into the ground, it freezes, and as it freezes, it expands to fill the space underground," said Flisfeder.

"Once it's reached kind of beyond the limits of those crevices, it has a tendency to push out even more and can make small fissures underground."

Not like an earthquake

Frost quakes are uncommon and are reported more in northern regions, he added. They're not confirmed by Environment Canada and are often left recorded as "word-of-mouth reports."

Ottawans last reported hearing frost quakes in December 2017, and there have only been a couple of occurrences in the past decade, he said.

Flisfeder said while the quakes cause popping sounds that can startle many, they aren't dangerous. Those fissures aren't typically strong enough to shake foundations of homes, he said.

"The coldest time of night is when they generally occur," he said. "It's not the same as an earthquake, where the ground would shake and you would want to get to a sound structure for protection. It's usually a very benign occurrence but can be startling."

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